[Sidefx-houdini-list] export 2d track to 3d

jose fernandez jose.fernandez at framestore-cfc.com
Mon Mar 17 13:19:34 EDT 2008


Ok, but would you then bring in the grid into chops using a geometry 
chop? Or what would you suggest to creep the point?

Louis Dunlevy wrote:
> The short hacky answer is just parent it to the camera, make it the same 
> aspect ratio as your plate and move it down z 'till it looks right! 
> Works 99% of the time ;)
>
> I always use the same camera frustrum asset so I don't have to think 
> about it too much.. all those numbers..
>
> jose fernandez wrote:
>   
>> How can I automatically fit a grid to camera, regardless of it's 
>> distance on Z (what expression could I use)?
>> Louis Dunlevy wrote:
>>   
>>     
>>> If you have the channels normalized in CHOPs all you need to do is fit a 
>>> grid to the camera and creep a point driven by chops onto it. There are 
>>> lots of ways to approach it but it kinda boils down to that type of thing..
>>>
>>> jose fernandez wrote:
>>>   
>>>     
>>>       
>>>> Well basically have a point in an arbitrary place in 3d space, that 
>>>> moves proportionally in screen space as the 2d track. no matter where 
>>>> the camera is...
>>>>
>>>> brian goodwin wrote:
>>>>   
>>>>     
>>>>       
>>>>         
>>>>> There many solutions to this,
>>>>> but to get a better idea of what u are trying to achieve,
>>>>>
>>>>> are you trying to use the 2D track in 3 Dimentions or just have a flat plane
>>>>> with locators that move on that flat place?
>>>>>
>>>>>
>>>>>
>>>>> On Mon, Mar 17, 2008 at 3:09 PM, jose fernandez <
>>>>> jose.fernandez at framestore-cfc.com> wrote:
>>>>>
>>>>>   
>>>>>     
>>>>>       
>>>>>         
>>>>>           
>>>>>> Hi I'm trying to export a 2d track into 3d space. I've brought in the
>>>>>> data through chops and fitted it to uv space (0-1) through a range node
>>>>>> (1-2048 in x, 1-1556 in y).
>>>>>> My first try was to use a grid at a certain point to project uv
>>>>>> cordinates from camera... and transferring attributes between chops and
>>>>>> the grid with point sops and finally a transfer attribute that copies
>>>>>> color with the 3d information in it to the tracking point. In short this
>>>>>> technique worked, but the metaball sampling doesn't seem to be accurate
>>>>>> enough and while the point is at the expected position I get random
>>>>>> jumps every few frames as it moves. I've tried playing with the kernel
>>>>>> values but nothing makes it better.
>>>>>> Could any ones suggest a more intelligent (and accurate) approach?
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>>>>>>     
>>>>>>       
>>>>>>         
>>>>>>           
>>>>>>             
>>>>>   
>>>>>     
>>>>>       
>>>>>         
>>>>>           
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